This week we have seen the resurgence of violence in Northern Ireland, with IRA splinter groups claiming credit for the murders of a police officer and two soldiers. And we have seen middle-aged men - sometimes alone and sometimes standing shoulder to shoulder - making pronouncements, issuing condemnations and calling for co-operation with the police in the investigations.

But hearing Sinn Fein Deputy First Minister Martin McGuinness' unprecedented call for co-operation with the police reminded me of the McCartney sisters, who led a campaign for justice after the 2005 murder of their brother Robert. The investigation was immediately hindered by an impromptu riot at the scene of the crime. Sinn Fein's initial response focused on the Police Service of Northern Ireland's use of riot police to try to access the crime scene. Sinn Fein politician Alex Maskey said: 'It appears the PSNI is using last night's tragic stabbing as an excuse to disrupt life within this community.'

The publicity around the McCartney campaign pressured the IRA and Sinn Fein into expelling a number of their members over the murder, with the IRA even publicly offering to shoot the suspects. But the sisters instead sought arrest and conviction. They criticised Sinn Fein because, like the 70 people who claimed to be in the pub toilet at the time, two of its council candidates were among those who saw nothing. At that time McGuinness warned the sisters against bringing politics into the matter.

It took two years for Sinn Fein President Gerry Adams to publicly call for co-operation with the police. The suspects were eventually found not guilty in court due to the lack of witnesses and forensic evidence.

This week's statements from McGuinness and Adams have been sincere, but there is a difference between honesty and sincerity that politicians often forget. You can't fake honesty. And excessive sincerity when honesty is required is the reason politicians are so mistrusted.

- Alex Hilton is a Labour parliamentary candidate and founder of political blogs Labourhome and Recess Monkey